The present invention relates generally to progressive multifocal ophthalmic lenses and, in particular, to a new construction for the refractive surface of a progressive multifocal lens for use preferably by an older person. As a person grows older, the amplitude of accommodation of the eyes becomes weakened. The present invention provides lenses which compensate for the weakened eye condition, such as presbyopia, and also provides spectacles utilizing such progressive multifocal lenses.
Conventional progressive multifocal opthalmic lenses are disclosed in Maitenaz U.S. Pat. No. 3,910,691 issued on Oct. 7, 1975 and in Winthrop U.S. Pat. No. 4,062,629 issued on Dec. 13, 1977. A progressive multifocal ophthalmic lens generally includes a portion for viewing distant objects at the upper position of the lens and a portion for viewing nearby objects at the lower position of the lens. An intermediate section is presented between the upper and lower portions. The three portions are known generally as the far vision viewing zone, the near vision viewing zone and the intermediate vision viewing zone. The zones are generally divided into left and right parts by a principal meridian curve which generally extends vertically. In at least the intermediate zone, the surface power varies progressively. The demarcations of each vision viewing zone are made to be smooth so that changes from one zone to the other by the eye are not perceived by the wearer of the lens.
It is desired to provide an improved progressive multifocal lens and spectacles using same which achieve each of the objects, benefits and advantages detailed below.